Production of monocarboxylic acids from large ring alicyclic alcohols



3,121,728 PRQDUCTTON U1 MCNUCARBQXYLIC AClDS FRCM LARGE illNG ALTCYCLIC ALCQHOLS .letirey ll. Bartlett, New Providence, and Samuel B. Lippincett, Springfield, P ll, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed May 26 196i), Ser. No. 30,453

11 Claims. (Cl. 260-413) The present invention relates to an improved process for preparing straight chain monocarboxylic acids and salts of these acids. More particularly this invention relates to reacting cyclic secondary alcohols with caustic alkali at high temperatures to obtain high yields of the alkali metal salt of the corresponding straight chain monocarboxylic acid. This salt may of course then be hydrolyzed to the acid if desired. Yet more particularly this invention relates to incorporating said salt into a lubrieating oil in grease making proportions. Most particularly this invention relates to an improved method of preparing lubricating greases wherein caustic fusion of a cyclic secondary alcohol is carried out in the presence of a lubricating oil.

According to the present invention it has now been discovered that cyclic secondary alcohols may be fused with caustic to obtain high yields of the corresponding straight chain monocarboxylic acid salts. This discovery is surprising since prior to the present it Was believed that only primary aliphatic alcohols (including those wherein one of the carbon atoms in the aliphatic chain is part of a ring compound) could be fused with caustic to obtain a monocarboxylic acid salt having the same number of carbon atoms as the starting material. Thus, for example, in US. 2,384,817 it is stated at page 1, column 1, lines 22 and 23, the reaction is applicable only to primary alcohols it has now been discovered that cyclic secondary alcohols can be reacted as described below to obtain both formation of the monocarboxylic acid salt and opening of the ring. Thus, for example, the equation for reacting cyclododecanol with caustic is presented below:

OHrOHrCHrUIIz-GHz-CH union CHKCHzhgCOONa Hz H oH oHrOm-GHro 011 Aside from the wide utility which the present invention will have for the preparation of any mono basic aliphatic acid from the corresponding cyclic secondary alcohol the present invention is of particular importance in that it provides an additional method for preparing cheap raw materials for grease production. T hus, prior to the present primarily only naturally occurring esters of fats and oils have been used in the manufacture of these soap thickened greases.

The present invention is of additional importance in view of the recent discovery that butadiene can be trimerized to 1,5,9-cyclododecatriene or dimerized to 1,5-cyclooctadiene in the presence of a metallo organo catalyst such as a titanium comprising catalyst. Thus, the process for preparing cyclododecatriene or cyclooctadiene is described for example in Angewandte Chemie, vol. 69, column 11:397 (June 7, 1957). According to this process both extremely high conversions and selectivities are obtained to the desired products. These materials can then be converted to the saturated alcohols by well known methods. Thus, for example, cyclododecatriene can be cheaply converted by selective hydrogenation as described in SN. 804,606 to cyclododecene which may then be hydrated to cyclododecanol with a strong acid such as H 50 Thus, a C cyclic secondary alcohol is cheaply prepared which can then be converted to the correspondi United States Patent 0 3,lZl,'iZ3 Patented Feb. 18, 1964 2 ing straight chain monocarboxylic acid in accordance with the process of this invention.

The alcohols used in this invention are cyclic secondary alcohols. Thus, in general they have the formula given below.

In this formula n is a number from 2 to 30 and each R and R is a radical selected from the group consisting of C to C alkyl groups and a hydrogen atom. In general the total number of carbon atoms in the alcohol will be in the range of 4 to 60. Thus, examples of these alicyclic secondary alcohols which may be reacted are the unsubstituted cyclic secondary alcohols such as cyclopentanol, cycloheptanol, cyciohexanol, cyclooctanol, cyclodecanol, cyclododecanol, cyclopentadecanol, cycloeicosanol, cyclotriacontanol, etc. Examples of the substituted mono cyclic secondary alcohols are nonylcyclo hexanol, 2,3- or trnethylcyclohexanol, or mixed methyl cyclohexanols obtained for example by hydrogenation of mixed cresols, dodecylcyclohexanol, methylcyclododecanol, dimethylcyclododecanol, decylcyclododecan-ol, methylcyclohexadecanol, 3,5,5 trimethylcyclohexanol, etc. Nonylcyclohexanol for example may be prepared from the commercially widely available nonylphenol by hydrogenation. In all of the substituted compounds the alkyl group may of course be attached to any of the carbon atoms of the ring.

The present process is carried out at temperatures in the range of 250 to 375 C., preferably 300 to 360 C., specifically 320 to 350 C. The pressures which may be used are from atmospheric to atmospheres, in general atmospheric pressure being satisfactory. The caustic alkali materials which may be used are the alkali metal hydroxides and the free alkali metals themselves. If free metals are used then water or steam must be injected at high temperatures to form the caustic in situ. In general NaOH and KOH and mixtures of these materials are preferred. Amounts of caustic alkali utilized should be in the range of 0.8 to 4 moles based on alcohol, preferably 1 to 3 moles, specifically 1.5 moles. Although it is preferred to carry out the reaction under generally anhydrous conditions in the presence of solid caustic alkali it is also of course contemplated that aqueous alkali solutions may be used.

In practice, it is desirable to mix the reactants and to heat the resultant mixture until a substantial evolution of hydrogen occurs, as evidenced either by its escape from the reaction zone or by the rate of increase of pressure it the system is closed. The temperature can be either held at this point or increased somewhat if a more rapid rate of reaction is desired. Completion of the reaction will be apparent from the decrease in the rate of hydrogen evolution, at which time approximately the theoretical quantity of gas will be found to have been given oil.

Certain metals, notably carbon steel, have a detrimental effect on the reactions, and appear to affect adversely the yield of desired products. Chromium alloys of iron and the nickel-containing so-called stainless steels are relatively free from this defect. Accordingly, While it is desirable to avoid the contact of unalloyed iron and ordinary steel with the reaction mixtures some types of stainless steel may be used. However, it is better to use reactors made of nickel or nickel alloys such as Hastelloy or Inconel. Vessels formed or lined with copper or copper alloys or with cadmium are most advantageous for use in the conduct of the reaction, and are preferred. When a copper or copper-lined vessel is used with cadmium catalysts, its surface soon becomes plated with cadmium.

Additionally it may be desired to add a small amount of a catalyst to improve reaction rates and to lower temperatures required in reaction. Catalysts which may be used are cadmium, copper, silver, ni kel, lead and zinc, cadmium being preferred. to amount of the catalyst used may vary widely and even traces of catalyst exert a discernible effect. It may be advantageous to add fresh portions of catalyst to the mixture during the course of the reaction to maintain a desired rate of reaction and to insure its completion. For most practical purposes the range of catalyst proportions are in the range of 1 atom of catalyst metal for each to 1000 hydroxyl groups. These catalysts may be supplied either as free metals or as their salts. With or without the addition of a catalyst it may also be desired to add a solvent to the reaction zone to increase contacting and thus improve reaction rates. Suitable solvents are high boiling saturated petroleum hydrocarbons (those boiling above 320 C.) e.g. white oils.

The salt of the acid may be recovered from the reaction zone directly or may be purified of unreacted materials by cg. dissolving it in water, or a WElf6f-C C alcohol mixture. Thus, the salt of the acid is dissolved in the aqueous solution and the salt is then recovered by evaporation or distillation. Further purification may be obtained if desired by contacting the Water layer with a light hydrocarbon such as a petroleum ether to remove unreacted alicyclic alcohols or other oil soluble products. Where the free acid is desired the water-alcohol solution or the caustic fusion product itself may be acidified with a mineral acid, e.g. H 30 HCl, thus springing the monocarboxylic acid which is then separated, e.g. by distillation.

In a preferred embodiment the process of the present invention is used to prepare lubricating greases. Lubrieating greases normally consist of lubricating oils thickened by alkali and alkaline earth metal soaps or other thickeners to a solid or semi-solid consistency. The soaps are generally prepared by the neutralization of high molecular weight fatty acids or by the saponification of fats which is usually carried out in a portion of the oil to be thickened.

The use of cyclic secondary alcohols as a grease-making material introduces no complication into the grease making procedure. While alkali fusion of the alcohol may be carried out in a separate preliminary acid-forming stage, the greases are preferably produced essentially in a single process step in which the cyclic secondary alcohol is fused with alkali in the lubricating oil base in grease-making proportions and at grease-making conditions, although at somewhat higher temperatures. At the conclusion of the fusion process a finished grease is obtained.

The alcohols which will be used in these preparations of greases Will in general be higher molecular weight materials such as cyclododecanol, cyclohexadecanol, cycloctadecanol, etc., preferably cyclododecanol due to its ease of preparation and cheapness. Thus C -C cyclic alcohols are preferred.

When carrying out the alcohol fusion in the lubricating oil itself so as to form the grease thickening salts in situ in accordance with the preferred embodiment of the invention, it has been observed that the alkali has a strong tendency to settle out of the reaction mixture to the bottom of the reactor in the form of a cake which does not fully participate in the reaction. Highly efficient stirring or agitation will counteract this tendency. However, in many cases more efficient stirring is required than may be obtained in conventional grease kettles and special equipment would have to be used.

It has been found that the settling tendency of the alkali in the lubricating oil-alcohol mixture is negligible when a sufficient amount of a solid suspending agent is present in the reaction mixture. Most desirable suspending agents are those which serve simultaneously as grease thickeners, such as soaps of high molecular weight fatty acids, silica gel, carbon black, bentones, Attapulgus clay modifications, etc.

Soaps, particularly sodium soaps of high molecular weight fatty acids are preferred for this purpose. However, the melting points of most of these soaps in lubricating oil is rather low, usually below 409 F. Thus, at the high reaction or fusion temperature of about 500 F. or thereabove, these soaps are liquid when used as such and do not entirely counteract the settling tendency of the alkali. This difficulty may be overcome by using the salt, preferably the alkali metal salt, of a low molecular weight acid in addition to the high molecular weight fatty acid soap. In this manner, soap-salt complexes are formed which melt well above 500 F. and thus form an excellent suspending agent.

These soaps or soap-salt complexes are preferably formed in situ by neutralization of the corresponding acids in the alcohol-oil mixture with alkali added in amounts sufiicient for this neutralization and the subsequent fusion which takes place at considerably higher temperatures.

igh molecular weight acids useful for this purpose include hydrogenated fish oil acids, C C naturally occurring acids of animal or vegetable origin, etc. These acids may be used in amounts ranging from about 230 wt. percent based on the finished product. Suitable low molecular weight acids include acetic, furoic, acrylic and similar acids to be used in proportions of about 1-10 wt. percent based on the finished product. Esters of the high and/or low molecular weight acids, particularly those containing mono basic acid esters may be used in place of the free acids in corresponding proportions. In this case, the alcohol portions of the esters are converted into acids and the corresponding soaps by alkali fusion. If esters of low molecular weight alcohols are used, elevated pressures may be employed to prevent volatilization of the alcohols. Of course, esters of non-volatile low molecular weight alcohols, such as poly-hydroxy alcohol esters, e.g. sorbitol acetate, glycol acetate, etc. may be used. Particularly the high molecular weight type of acids or their esters used for this purpose may also be prepared by alkali fusion of Oxo products.

The salts formed by alkali fusion of the alcohols herein described in the presence of other fatty acid soaps consistently yield excellent smooth greases. Other conventional thickeners, anti-oxidants, corrosion inhibitors, tackiness agents, load-carrying compounds, viscosity index improvers, oiliness agents, and the like may be add-ed prior, during and/or after the fusion process as will be apparent to those skilled in the art.

The base oil used as menstruum during the fusion process should be a mineral lubricating oil. After the fusion is completed, synthetic lubricating oils, such as a dibasic acid ester (eg. di-2-ethyl hexyl sebacate, adipate, etc), polyglycol type synthetic oils, esters of dibasic acids and polyhydric alcohols, etc, as well as alkyl silicates, carbonates, formals, acetals, etc. may be used alone or in addition to mineral lubricating oil to bring the grease to the desired consistency. The oil base preferably comprises about 50 to about of the total weight of the finished grease.

As indicated above, the process of the invention may be carried out in two stages. When so operating, the alcohol to be fused may be added over a period of several hours, say 5l5 hours, in substantially stoichiometric proportions, to a molten mixture of alkali and mineral oil, preferably a heavy oil, maintained at fusion temperatures of, say, about 230320 C. When all the alcohol has been added, heating may be continued at these temperatures until gas evolution substantially cease. The acid formed may be recovered from the reaction mixture after cooling, by dilution with water followed by extraction of the oil and any unreacted alcohol with a light hydrocarbon solvent, such as pentane, hexane, heptane or the like, and acidification of the aqueous railinate. If desired, the free acid may be purified by vacuum distillation. The acid so prepared may then be introduced into a lubricating oil base stock, other high and/ or low molecular weight fatty acids as well as other grease additives may be added and the mixture may be converted into a grease by the addition of at least sutlicient caustic alkali, preferably in aqueous solution, to neutralize the acids present. Conventional grease making conditions including temperatures of about 180260 C. may be used in this stage. The salt derived from the alcohol by alkali fusion should form at least wt. percent and preferably about 30-50 wt. percent of the grease thickener or about 20-20 wt. percent of the finished grease. The remainder of the grease thickener is preferably made up by a suitable soap-salt complex of type described above. The proportion of soap derived from alcohol to soaps and salts derived from other acids may be about 1:4 to 4:1 and preferably is about 1:1.

In order to prepare a grease by alkali fusion of the alcohol in situ in accordance with a more desirable embodiment of the invention, the grease making procedure may be quite generally as follows. A mineral lubricating oil base is mixed with solid alkali, preferably in flake or pellet form. The mixture is heated to about 230 260 C. whereupon the alcohol is slowly added in increments or continuously over a period of about l-20 hours under vigorous stirring. A reaction temperature of about 250-320 C., preferably about 260305 C., is maintained throughout the alcohol addition. After all the alcohol has been added, heating at these temperatures is continued until evolution of hydrogen ceases or until the desired conversion has been obtained. The reaction mixture is quenched or allowed to cool and may then be diluted with further amounts of lubricating oil to the desired grease consistency.

A similar procedure is employed when the alcohol is subjected to alkali fusion in situ in the presence of suspending agents, such as soaps of high molecular weight fatty acids or complexes of such soaps with low molecular weight fatty acids salts in accordance with the preferred embodiment of the invention. :In this case, all the acids needed to form the suspending agent are added to the mineral oil together with the alcohol. Thereafter, suifb cient caustic alkali to neutralize the acids and convert the alcohol to salt is added, preferably in the form of an aqueous solution of about 4050% and the mixture is heated at a saponification temperature of about 150 205 C. until the acids are converted to soaps and salts and all the water is volatilized. Alkali fusion is then carried out substantially as described above, except that less violent stirring is required.

The present invention will be more clearly understood from a consideration of the following examples.

Example 1 A one gallon nickel reactor, equipped with a stirrer, thermometer, feed line and condenser was charged with 300 g. Primol D solvent (is. a highly acid treated naphthenic mineral oil having a boiling range between 395520 C.), 108 g. NaOH pellets and 94g. KOH pellets. After heating the mixture to 320 C., 91 g. of cyclododecanol dissolved in 600 g. of Primol D was added gradually during 45 minutes with the temperature at 320 to 370 C. For most of this period the tem erature was at 350360 C. During the course of the reaction 0.6 cu. ft. of gas were evolved.

After allowing the reactor to cool to 270 C. the product was removed by suction and dispersed in 4 liters of water to which was added 500 cc. isopropyl alcohol. This mixture was given three extractions with petroleum ether. The remaining aqueous layer was acidified with HCl and the acid removed by extraction with petroleum ether. On evaporation a residue of 64 g. of crude acid was obtained. T he crude acid mixture was then esterified with methanol using toluene sulfonic acid as a catalyst. The ester was washed with 5% NaOl-l and then with water and then evaporated on the steam bath. The total ester recovered was 51 g. which was distilled through a spinning band Example II.--Preparati0n of Sodium Soap Thickened Grease by Fusion of Cyclododecanol in Mineral Oil Formulation:

Ingredients Percent weight Cyclododecanol 10.0 Hydrofol acids 51 1 10.0 Glacial acetic acid 4.0 Sodium hydroxide 7.0 Phenyl 0c naphthylamine 1.0

Diol 55 68.0

Hydrofol acidsnre hydrogenated fish oil acids having a tliegree of saturation corresponding to commercial stearic act Diol 55 is a base cut oil from a hydrofined low cold test coastal crude having a viscosity at 40 C. .500 SSU.

Preparation: The cyclododecanol, Hydrofol Acids 51 and the Mineral Oil (Diol 55) were charged to a fire treated kettle and intimately mixed. To the mixing materials was added the acetic acid followed immediately with a 40% aqueous solution of the sodium. hydroxide. The heat of reaction caused the temperature to rise to 60 C. whereupon heating was initiated and the temperature was raised to 370 C. The time above 260 C. is given as follows:

Minutes: Temperature, C. O 260 10 290 20 320 40 330 50 345 55 360 70 1 370 260 1 Heating discontinued.

During the cooling cycle the phenyl or naphthylamine was added at 120 C. and the grease further cooled to C. A sample taken for free alkalinity showed an excess of 1.0% calculated as NaOH. This free alkalinity was reduced to 0.4% by the addition of sufficient Hydrofol Acids 51 (3.0% sodium hydroxide) as a 40% aque ous solution, the water being boiled oil from the grease. Tlhe grease was finished by Morehouse Milling at 0.005 c earance.

Properties:

Appearance Excellent, smooth homo geneous product. Dropping point, F 500+. Penetrations, 77 F.

Unworked 265.

Worked, 60 strokes- 270.

Worked, 10,000

strokes 269.

Water solubility Soluble. Wheel hearing test Pass.

Slump None.

Leakage grams"--- 0.0. Normal Hotfmann oxidation hours to 5 p.s.i. drop in O 198.

Lubrication life hours,

250 F.10,000 rpm. 2000+.

of about In the above preparation, the cyclododecanol shows a conversion to the sodium salt of approximately 64.5%. This is desirable in that the remaining unconverted cyclododecanol remains as a plasticizer preventing the ex tremely hard product when all the alcohol is converted.

Example ZII.Caustic Fusion of Cyclolzexanoi A one gallon nickel reactor equipped with a stirrer, condenser, thermometer and feed line was charged with:

Primol D 700 NaOl-I flakes 370 KOH flakes 330 After heating the above mixture to 345 C., 600 g. cy-

clohexanol were added gradually during hours at 325 to 345 C. This mixture was allowed to cool to 290 C. and then removed from the reactor by means of suction. During the reaction 6.28 cu. ft. of gas was evolved which was measured by means of a wet test meter. The total product removed from the reactor was 1780 g. which was added to 6 liters of water. This was then given three extractions with petroleum ether to remove Primol D and any unreacted cyclohexanol. The aqueous layer was then acidified with HCl and the crude acid layer removed and evaporated on the steam bath to remove traces of petroleum ether. Yield=504 g. of crude evaporated acid having an acid number of 439.8 mg. KOH/ g.

A portion of the crude acid (500 cc.) was distilled in an Oldershaw column at /1 reflux ratio (30 theoretical plates). In the distillation 368 cc. were obtained with a boiling point of 198-2065 C. which is in the range of caproic acid having an acid number of 479.1 mg. KOH/ g. (theoretical for caproic acid=482.9 mg. KOH/gm.).

Example Il .Caustic Fusion 0 3,5,5 Trimethylcyclohexaizol The same reactor as used in Examples I and III was charged with:

800 g. Primol D 555 g. NaOH pellets 500 g. KOH pellets After heating the mixture-to 320 C. there was gradually added 1500 g. 3,5,5 trimethylcyclohexanol during 2 hours with the temperature being maintained at 320340 C. The resulting product was allowed to cool to 270 C. during 1 hour, then removed from the reactor by means of suction. There were 84 ml. water removed during the reaction and 15.65 cu. ft. of gas evolved.

A total of 2669 g. of material was removed from the reactor and it was poured into a mixture of 8 liters of water and 1 liter of isopropyl alcohol. The resulting mixture was given three extractions with petroleum ether, then the aqueous layer was acidified with HCl to spring the acids. Removal of the acids was facilitated by dissolving in petroleum ether which was later evaporated leaving a residue of 1171 g. of crude acids having an acid number of 305 mg. KOH/gm. A 975 g. portion of the acid was distilled and a main cut of 531 g. was obtained boiling @152l57 C. 50 mm. having an acid number of 339.4 mg. KOH per gm. and a hydroxyl number of 16 mg. KGH per gm.

It is to be understood that this invention is not limited to the specific examples, which have been otiercd merely as illustrations, and that modifications may be made without departing from the spirit of this invention.

What is claimed is:

l. A process for preparing an alkali metal salt of an aliphatic monocarboxylic acid which comprises reacting a cyciic secondary alcohol represented by the formula presented below wherein n is a number from 2 to 30 and each R and R is a radical sel cted from the group consisting of C to C alkyl groups and a hydrogen atom, with caustic alkali at temperatures in the range of 250 to 375 C., the amount of caustic alkali being in the range of 0.8 to 4 moles per mole of alcohol and recovering an aliphatic monocarboxylic acid having the same number of carbon atoms as said cyclic secondary alcohol.

2. The process of claim 1 in which the caustic alkali is sodium hydroxide.

3. The process of claim 1 in which the caustic alkali is potassium hydroxide.

4. The process of claim 1 in which the caustic alkali is a mixture of sodium hydroxide and potassium hydroxide.

5. The process of claim 1 in which each R and R is a hydrogen atom.

6. The process of claim 1 in which at least one of the Rs is an alizyl group.

7. The process of claim 1 in which at least one of the Rs is a branched alkyl group.

8. The process of claim 1 in which the total number of carbon atoms in the alcohol reacted is 4 to 60.

9. The rocess of claim 1 in which the cyclic secondary alcohol is cyclododecanol.

1 3. The process of claim 1 in which the cyclic secondary alcohol is nonylcyclohexanol.

11. A process for preparing an aliphatic monocarboxylic acid which comprises reacting a cyclic secondary alcohol represented by the formula presented below wherein n is 2 to 30 and wherein each R and R is a radical selected from the group consisting of C to C alkyl groups and a hydrogen atom, with caustic alkali at temperatures in the range of 250 to 375 C., the amount of caustic alkali being in the range of 0.8 to 4 moles per mole of alcohol, and hydrolyzing the reaction roducts to liberate free acid from the acid salt and recovering an aliphatic monocarboxylic acid having the same number of carbon atoms as said cyclic secondary alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 1,926,068 Strosacher et al. Sept. 12, 1933 2,727,050 Sutton Dec. 13, 1955 2,766,267 Hill Oct. 9, 1956 2,801,972 Bartlett et al. Aug. 6, 1957 2,801,974 Morway et al. Aug. 6, 1957 2,926,182 Sutton Feb. 23, 1960 

1. A PROCESS FOR PREPARING AN ALKALI METAL SALT OF AN ALIPHATIC MONOCARBOXYLIC ACID WHICH COMPRISES REACTING A CYCLIC SECONDARY ALCOHOL REPRESENTED BY THE FORMULA PRESENTED BELOW 